kvm: ppc: detect old headers

When compiling Qemu with older kernel headers, the PVR setting
mechanism isn't available yet. Unfortunately, back then I didn't add
a capability we could check against, so all we can do is add a configure
test to see if we support PVR setting. For BookE, we don't care yet.

This fixes compilation errors with KVM enabled on older kernel headers
(like 2.6.32).

Signed-off-by: Alexander Graf <agraf@suse.de>

configure

@@ -1771,6 +1771,21 @@ recent kvm-kmod from http://sourceforge.net/projects/kvm."
   fi
 fi
 
+##########################################
+# test for ppc kvm pvr setting
+
+if test "$kvm" = "yes" && test "$cpu" = "ppc" -o "$cpu" = "ppc64"; then
+            cat > $TMPC <<EOF
+    #include <asm/kvm.h>
+    int main(void) { struct kvm_sregs s; s.pvr = 0; return 0; }
+EOF
+    if compile_prog "$kvm_cflags" "" ; then
+        kvm_ppc_pvr=yes
+    else
+        kvm_ppc_pvr=no
+    fi
+fi
+
 ##########################################
 # test for vhost net
 
@@ -3257,6 +3272,9 @@ case "$target_arch2" in
       if test $vhost_net = "yes" ; then
         echo "CONFIG_VHOST_NET=y" >> $config_target_mak
       fi
+      if test $kvm_ppc_pvr = "yes" ; then
+        echo "CONFIG_KVM_PPC_PVR=y" >> $config_target_mak
+      fi
     fi
 esac
 if test "$target_bigendian" = "yes" ; then

target-ppc/kvm.c

@@ -94,19 +94,33 @@ static int kvm_arch_sync_sregs(CPUState *cenv)
     int ret;
 
     if (cenv->excp_model == POWERPC_EXCP_BOOKE) {
+        /* What we're really trying to say is "if we're on BookE, we use
+           the native PVR for now". This is the only sane way to check
+           it though, so we potentially confuse users that they can run
+           BookE guests on BookS. Let's hope nobody dares enough :) */
         return 0;
     } else {
         if (!cap_segstate) {
-            return 0;
+            fprintf(stderr, "kvm error: missing PVR setting capability\n");
+            return -ENOSYS;
         }
     }
 
+#if !defined(CONFIG_KVM_PPC_PVR)
+    if (1) {
+        fprintf(stderr, "kvm error: missing PVR setting capability\n");
+        return -ENOSYS;
+    }
+#endif
+
     ret = kvm_vcpu_ioctl(cenv, KVM_GET_SREGS, &sregs);
     if (ret) {
         return ret;
     }
 
+#ifdef CONFIG_KVM_PPC_PVR
     sregs.pvr = cenv->spr[SPR_PVR];
+#endif
     return kvm_vcpu_ioctl(cenv, KVM_SET_SREGS, &sregs);
 }